One of my best places to learn notes is in the kitchen. If you have a well-stocked spice rack, start there. I already liked to cook when I started here, so I was golden. As for other notes, just take opportunities as they come. When I'm in home depot, i'll sometimes discreetly smell the cedar racks...etc.
Also, there are many "one note" fragrances that are designed to display only a certain note. Usually if you type in the name of the note in the title of the fragrance prompt in the directory seach engine, you'll get a list of niche frags that revolve around that note. You'll figure out which are the most accurate representations by reading the reviews. Try Tam Dao by Diptyque for a sandalwood demonstration (it wouldn't come up in a "sandalwood" title search, so i'll tell you here). Or search the name of the note in the community search. There are threads devoted to most of the "main" notes that will have many reccommendations. Then order samples!!